A handheld electronic nose (e-nose) based on metallo-tetraphenylporphyrin/carboxylic-functionalized singlewalled carbon nanotube (MTPP/SWNT-COOH) chemical gassensors has been demonstrated as a promising instrument for monitoring in food production process. In this work, the gas sensor array was fabricated by dispersing SWNT-COOH in the matrix of different MTPP compounds, namely, MnTPP, FeTPP, ZnTPP,CoTPP and CuTPP. The sensing responses were studied in terms of the changing sensor resistance under the atmosphere of various volatile compounds. The results show that the central metals in tetraphenylporphyrin (TPP) ring play a major role in the selectivity of each gas sensor to each volatile gas. We have investigated the functionality of this handheld e-nose by monitoring the odor of fermented rice during the 5-day fermentation process. Based on the principal component analysis, it was found that the handheld e-nose
can track the change of odors generated from the fermentation, in which largest odor change happens on the fifth day.